High-Efficiency Reconfigurable Single-Stage Bidirectional AC/DC Converter for 50 kW Fast Charger

Abstract

This article presents a reconfigurable single-stage AC-DC converter for fast Electric Vehicle (EV) battery charging. The proposed converter offers high power transfer capability, high efficiency, and a wide output voltage range of full Zero Voltage Switching (ZVS) turn-on, facilitated by its reconfigurable features and an additional control variable. Low rating relays are installed on the secondary side of transformers to diversify output battery voltages. These relays are pre-set before the charging process begins, based on EV battery class, as changing relays during the charging process could lead to dynamic issues due to its low-speed operation. In addition, control variables of the proposed converter are optimized to reduce switching losses, conduction losses, and grid current total harmonic distortion (THD). Therefore, the proposed converter provides efficient and reliable charging for both 400 V and 800 V class EV batteries. An 8.4 kW fast charger laboratory prototype module is built and tested to validate theoretical claims at grid input voltage of 230 V, and battery voltages from 150 V to 920 V. As a result, peak efficiency of 97.15% is achieved. Above all flat efficiency power conversion is achieved according to charging line.

Keywords

• Fast charger
• high efficiency
• reconfigurable single-stage AC-DC converter
• wide output voltage range